Embodiments of the present invention generally relate to optical measuring devices for testing a liquid sample, and more particularly to handheld optical measuring devices having immersible sensors for measuring one or more optical properties of a liquid sample.
Monitoring water quality, including various substances within a water sample, is a process widely used in many fields, and as will be appreciated, can be important in any application that relies on maintaining and/or changing various characteristics of a water sample. Some examples of relevant applications include monitoring natural water sources for environmental concerns, monitoring industrial water systems to ensure adequate performance, and monitoring municipal water systems to ensure quality criteria are met. Of the countless ways to test, characterize, and monitor water flows, measuring the optical properties of a water sample has become an important and reliable method for characterizing certain properties of the water sample. A number of methods are available for measuring the optical properties of a water sample.
Absorption spectroscopy can provide information about the range of electromagnetic spectra absorbed by one or more substances in a water sample. In using a spectrophotometer, ultraviolet and/or visible light at a certain wavelength (or range of wavelengths) is shined through the water sample. The spectrophotometer measures how much of the light is absorbed by the water sample. The concentration of the substance in a water sample can then be determined by measuring the intensity of the light transmitted through the water sample and calculating the concentration of the substance based on the measured water sample transmission.
Fluorometric spectroscopy concerns the detection of fluorescent light emitted by a sample of interest. It involves using a beam of light, usually ultraviolet (UV) light, that excites the electrons in molecules of certain compounds in the sample and causes them to emit light of a lower energy (i.e., to “fluoresce”). There are several types of fluorometers for measuring emitted fluorescence. Fluorometers generally have of a source of excitation radiant energy, an excitation wavelength selector, a sample cell to contain the sample material, an emission wavelength selector, a detector with signal processor and a readout device. Filter fluorometers use optical filters to isolate the incident light and fluorescent light. Spectrofluorometers use diffraction grating monochromators to isolate the incident light and fluorescent light.
One method of monitoring the concentration of a chemical product (e.g., a cleaning agent) within a water sample relies on monitoring the fluorescence of the product that occurs when the sample (and the product within the sample) is exposed to a predetermined wavelength of light. For example, compounds within the product or a fluorescent tracer added to the product may fluoresce when exposed to certain wavelengths of light. The concentration of the product can then be determined using a fluorometer that measures the fluorescence of the compounds and calculates the concentration of the chemical based on the measured fluorescence. Such determinations can be especially important in cleaning and antimicrobial operations in which commercial users (e.g., restaurants, hotels, food and beverage plants, grocery stores, etc.) rely upon the concentration of the cleaning or antimicrobial product to make the product work effectively. The same may be true for other applications, such as water care, pest control, beverage and bottling operations, packaging operations, and the like.
Turbidity sensing provides a quick, practical indication of the relative amount of suspended solids in water or suspended liquids. Many industrial and commercial bath applications can make use of turbidity and conductivity sensing to improve product quality, minimize ingredient consumption, and reduce wastewater discharge. Turbidity sensors often determine the amount of suspended solids based on the amount of light transmitted through a sample or scattered by a sample.
Other methods of measuring and monitoring optical properties of a water sample are also available.